1. Field of the Invention
The present invention relates to methods and devices for analyzing the character and properties of surfaces. In particular, it relates to devices for optically scanning otherwise inaccessible surfaces. The system is especially useful for but not limited to monitoring interior surfaces of objects, such as manifolds, for coating deficiencies, cracks and other irregularities.
2. Description of the Prior Art
Non-visual inspection of devices and materials for defects and quality control by X-rays has proved at times to be both harmful to operating technicians and destructive to the materials under inspection.
Optical scanning avoids the deleterious effects of radiation. However, optical methods require direct access of the scanning beam to the surface to be inspected. Light rays will not penetrate solid surfaces and, for most practical applications, must be considered constrained to propagate in a straight line.
Many kinds of optical scanners have achieved satisfactory operation. A drawback common to prior art scanners has been the location of moving mechanical parts near the output of the scanner. Often, such design proves undesirable in terms of space availability, maintainability and reliability.
Methods of relaying the beam away from the scanner include hard optics (conventional lenses) and fiber optics. Hard optics does not have the ability to follow curved surfaces necessary in many applications. Conventional clad optical fibers can accommodate curved surfaces but do not preserve the phase of the laser beam wavefront. Hence, a laser beam scanned at the input to the fiber will not be reproduced at the output of the fiber.
The present invention overcomes these and other drawbacks of the prior art by providing an optical scanner which includes a flexible optical cable having mode-preservation properties partially mounted on a mechanical crawler to project and scan reflected laser beam light. A system of relay optics rotates and mode matches the laser beam into the cable.